Reversible circulation internal fan kiln



May 5, 1925. 1,536,735

R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Filed Oct. 24, 1933 3 Sheets-Sheet 1 000 00000 O 0O OO O O0 O0 00 00300 INVENTOR. FIG 3 RQLF THELEN A TTORNEY R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN May 5, 1925.

Filed 'Oct. 24, 1923 3 Sheets-Sheet 2 INVENTOR. ROLF THELEN FIG. 2

ATTORNEY May 5, 1925. 0

R. THELEN REVERSIBLE cmcuumou INTERNAL mm mm 3 Sheets-Sheet 3 Filed Oct. 24, 92

E oooooJhoK 00 0000 A 00 oo on INVENTOR.

OL.F TT-IELEN yflft 'T/tvb w.-

ATTORNEY Patented May 5, 192 5.

UNITED STATES ROLF THELEN, OF MADISON, WISCONSIN,

DEDICATED, BY'MESNE ASSIGNMENTS, TO

THE CITIZENS OF THE UNITED STATES OF AMERICA.

REVERSIBLE CIRCULATION INTERNAL FAN KILN.

Application filed October 24, 1923. Serial No. 670,568. (GRANTEDUND ER THE ACT OF MARCH 3, 1883; 22 STAT. L. 625.)

To all whom it may concern:

Be it known that I, ROLF THELEN, a citizen of the United States of America, and an employee of the Department of Agriculture,

residing in Madison, Wisconsin, whose postofi'ice address is Madison, Wisconsin, have invented a new and Improved Reversible Circulation Internal Fan Kiln.

This application is made under the act 10 of March 3, 1883, Chapter 143 (22 Ste t. 625), and the invention herein described and claimed may be used by the Governmentiof the United States. its officers and employees, and by any person in the United States with- 1 out the payment to me of any royalty thereon. I hereb dedicate the same to the free use of the rovernment and the people of the United States.

My invention consists in an improvement in the design of forced circulation kilns or chambers for drying and conditioning lum: her or similar material. However, its use is not limited to wood or wood products. It consists in the adaptation of fans of the 25 disk type, or similar types. to the production of a unique internal circulation of air and the vapor in the kiln combined with the production and regulation of the heat and the humidity within the kiln.

This invention is illustrated in Figures 1 to 5. Figure 1 represents a cross-sectional elevation. Figure 2 represents a horizontal cross-section taken at slightly different elevations in order to bring out more clearly some of the essential features; Figure 3 represents a verticallongitudinal cross-section near the center of one of the tracks and shows in detail some of theair distributing system. Figure 4 represents a cross-section 40 a1 elevation of a three-track modification with dampered diflusers; Figure 5 represents a portion of a dampered diffuser.

The principal feature which I claim as novel and an improvement over existing kilns is the use and arrangement of the fans and the air distributing system. This arrangement is such that a very fast and uniform circulation of air and vapor through the piles of lumber may be secured and per- 5 mits the periodic reversal of the direction of the air movement by simply reversing the direction of rotation of the fans. The air distributing system provides a very uniform flow of air throughout the length of the i kiln and eliminates the non-uniformity of drying, which is one of the commonest troubles experienced in the ordinary kiln. The arrangement of the fans upon two shafts extending throughout the length of the kiln provides a simple means of producing a brisk circulation; and the elimination of comparatively small ducts such as those used in external blower kilns reduces very materially the work required to produce a given circulation. The differences in air pressure required in the operation of this kiln are much smaller than those ordinarily required in kilns employing centrifugal blowers, and the disk fans operate very efiiciently' at these .low pressures. It is possible,ftherefore, by the use of this invention to produce a very great and uniform circulationof air and vapor within the kiln with a very small expenditure of power.

While it is obvious that there are many possible ways in which the use of internal fans can be adapted to drying kilns of different types, this invention is limited to kilns in which the lumber is fiat end piled and in which two rows of fans are employed.

Any well-known means of heating the air and the vaporin the kiln may be used in conjunction with this invention. WVhen steam pipes are used they may be arranged beneath the lumber piles or in any other convenient manner. Any convenient form and arrangement of heaters may be used.

The drawings show and the specification describes steam jet pipes for increasing the humidity, and air inlet flues with suitable dampers for decreasing the humidity.

lVhile the drawings show and the specification describes specific means for heating the .air and the vapor in the kiln and for regulating the humidity of the air in the kiln, this invention is not limited specifically to the arrangements described. but may make use of any other suitable and well-known means'for accomplishing the same purposes. While the drawings illustrate and the specification describes a specificform of fiat end piled lumber. the invention is not limited to this particular form since it is equally applicable to other forms of flat end piling, such as double piles with parallel-sided pile chimneys and single piles with pile chimneys over each air distributor and with or without a central air passage. It is also adapted to inclined piling in which the layers of lumber are inclined slightly from the horizontal to assist the air movement. When single end piling is used in place of the double end piling illustrated, the lumber supporting trucks or other means for supporting the lumber will normally extend from side to side of the kiln, and the two central tracks can be replaced by a single track.

Referring to Figures 1, 2, 3, 4 and 5, which are correspondingly lettered: AA represent the side deflecting partitions. These partitions serve to form a passageway for the air from the heating coils to the fans when the air circulation is in the drection indicated on Figure 1, and when ihe direction of the air circulation is in the opposite direction they serve to deflect the air de-.

livered by the fans toward the sides and center and over the heating coils. BB are the fans producing the circulation. These fans are of the disk or propeller type, with which the movement of the air is substantially parallel to the fan axis. CC are the shafts upon which the fans are mounted. Provision is made to take care of the expansion and contraction of these shafts with changes in the temperature in the kiln. 'DD are air inlet dampers used to regulate and control the amount of air entering the kiln from the outside. EE are the heating coils. The coils illustrated in the drawings and described in the specification are of the return bend type. This invention is, however, not limited to this type since any common or well-known type may be adapted to it. FF are the steam jet pipes used to increase the humidity of the air in the kiln. The two lower pairs are used when the circulation of the air and vapor is downward through the pile chimneys VV and the three upper pipes are used when the circulation is in the reverse direction. This particular arrangement of the steam jet pipes is designed to assist the fans inmaintaining the air circulation. Various other common or wellknown arrangements can be used. GG are the lumber-supporting trucks. H are the shaft hangers. II are bearings for the shafts CC. J J are the tracks upon which the lumber-supporting trucks run. This invention is not specifically limited to the form and arrangement of lumber-supporting trucks, tracks, and track-supports illustrated since any well known method of supporting the lumber may be used without influencing in any way the efiiciency or the operation of the kiln. K are the side walls of the kiln. LL is the lumber to be dried. MIM are the track supports. NN are the shaft pulleys. 00 are air outlet dampers for controlling the amount of air being exhausted from the kiln. PP are belts passing over the pulleys NH and QQ. QQ, are the motor pulleys. R is the motor which furnishes the powerfusers.

drawings show and the specification describes upwardly restricted chimneys, chim=- neys of other shapes, such, for instance, as

chimneys with parallel sides may be used.

W are the side air passages which may likewise be of any well-known form as well as the form illustrated in the drawings and described in the specification. XX are the main air distributors. YY are the upper diffusers and ZZ the lower diffusers. a is the central air passage. bb are dampers adapted to restrict the air passages in that form of diffuser illustrated in Figures 4 and 5. Each main distribntor'with its side deflecting partitions and the two sets of diffusers forms a single air deflecting and distributing unit.

The operation of the kiln is briefly as follows: The lumber is placed in the kiln, the doors and all of the dampers are closed, and the kiln is started. Steam is turned into the coils and one set of stem jets is turned on. Suitable regulating devices are provided to control and regulate the supply of steam to the heating coils and the supply of steam to the steam jets. If it is found impossible to reduce the humidity to the desired point with the steam jets all turned off, the dampers DD and 00 are opened to allow fresh air to enter and moist air to escape. These dampers are adjusted so that a humidity below that desired will be secured. The steam jets may-then automatically supply a sufiicient amount of steam to bring the humidity up to the desired point. If the directionof rotation of the motor, the shafts, and the fans is such that the air and'vapor pass upward through the pile chimneys VV, the air and vapor will pass laterally outward and inward through the lumber into the side passagesWW and the central air passage a respectively, downward through these passages, across the heating coils. past the side deflecting partitions, through the fans into the main air distributors which act as plenum chambers, a slight pressure being maintained through the action of the fans and the resistance of the upper and lower diffusers. The air and vapor then pass from the main air distributors through the lower diffusers ZZ. The resistance of the upper diffusers YY serves to maintain a slight plenum between the upper and lower dif- The air and vapor then pass upward through the upper diffusers and into pile chimneys VV, repeating the cycle continuously. The use of the two sets of diffusers in the manner indicated produces a very' uniform flow of air throughout the length of the kiln. The unbalancing effect of the horizontal air flow produced by the fans is practically eliminated by allowing a slight pressure to build up in the main distributors. This is still further eliminated by the slight plenum between the space between the upper and lower distributors. It is obvious that the kiln would work reason ably well with a single set of diffusers for each main air distributor and that still further uniformity in air distribution might be secured by adding a third or even a fourth set of diffusers. The principle, of course, remains the same and practical expediency "will determine the balance between increased uniformity of air distribution secured by the addition of more sets of distributors and the loss in efficiency which they cause. Two forms are illustrated: in Figures 1 and 3, the diffusers consist of parallel slats with air spaces of suitable width between them. In Figures 4 and 5 the diffusers consist of .plates perforated with holes of suitable size.

Dampers bb are provided to enable the size of the holes to be readily regulated, thus controlling the conditions in each plenum chamber.

It is well understood that when the circulation of the air in the kiln is continuously in one direction, that portion of the pile'at which the air enters will dry more rapidly than the opposite side since the air in its passage through the lumber picks up moisture and thus reduces its drying capacity. To overcome this defect, the direction of rotation of the fans may be reversed, thus reversing the direction of the motion of the air through the lumber piles. This may 'be done periodically every two or three days air passage to the pile chimneys. downward can be embodied in original:

through the pile chimneys, through the upper diffusers and lower diifusers, into the main air'distribu'tors; and thence back to the fans. When the air travelsin this direction the heating coils serve to act as distributors,

and by the time the'jair leaves the upper steam jet lines it has become distributed with sufficient uniformity.

Having fully described the principles of this invention and the manner in which they a' dry kiln, I claim as 1. In a dry kiln arranged for flatwise end vmeans for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; and two air distributing units, each comprising a main air distributor, side deflecting partitions, and two sets of diffusers.

3. In a dry kiln arranged for flatwise end piling: two series of fans; two shafts upon which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues;

means for heating the kiln and its contents;

and two air distributing units, each comprising a main air distributor, side deflecting partitions, and two sets of diffusers.

4. In a dry kiln arranged for flatwise end piling: two series of fans; two shafts upon which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; means for heating the kiln and its contents; means for humidifying the atmosphere in the kiln; and two air distributing units, each comprising a mainair distributor. side deflecting partitions, and two sets of diffusers.

5. In a dry kiln arranged for flatwise end piling: two series of fans; two shafts upon which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; a plenum chamber for each fan; and a diffuser with restricted discharge. passages for each plenum chamber.

6. In a dry kiln arranged for flatwise end piling: two series of fans; two shafts upon which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; damp-.

rection to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet fines and dampered air out let flues; means for heating the kiln and its contents; a plenum chamber for each fan; and a diffuser with restricted dis charge passages for each plenum chamber.

8. In a dry kiln arranged for flatwise end piling: two series of fans; two shafts upon which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; means for heating the kiln and its contents; means for humidifying' the atmosphere in the kiln; a plenum cham ber for each fan; and a diffuser with restricted discharge passages for each plenum chamber.-

9. In a dry kiln arranged for flatwise end piling: two series of fans; two shafts upon which the fans are mounted for rotation, means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; a series of plenum chambers for each fan; and a diffuser. with restricted discharge passages for each plenum chamber. I

10. In a dry kiln arranged for flatwise end piling: two series of fans: two shafts upon which the fans are mounted for rotation: means for rotating said shafts in either direction to cause reversal of the circula culation of the air and vapor in said kiln;

dampered air inlet flues and dampered air outlet flues; means for heating the kiln and its contents; a series of plenum chambers for each fan; and a difi'user with restricted discharge passages for each plenum chamber.

12. In a dry kiln arranged for flatwise .end piling: two series of fans; two shafts upon which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet fiues; means for heating the kiln and its contents; means for humidifying the atmosphere in the kiln; a series of plenum chambers for each fan; and a diffuser with restricted discharge passages for each ple num chamber.

13. In an internal fan dry kiln adapted for flatwise end piling: two series of fans; a plenum chamber for each fan; and a diffuser with restricted discharge passages for each plenum chamber.

14:. In an internal fan dry kiln adapted for flatwise end piling: two series of fans; a series of plenum chambers for each fan;

and a diffuser with restricted discharge passages for each plenum chamber.

15. In an internal fan dry kiln adapted for flatwise end piling: piles of lumber disposed in two rows to form upwardly-restricted pile chimneys and a vertical passage between said rows of lumber piles.

16. In an internal fan dry kiln adapted for flatwise end piling: piles of lumber disposed in two rows to form upwardly-restricted pile chimneys, a vertical passage between said rows of lumber piles, and a vertical passage between the latter and each of the side walls of the dry kiln.

17 The herein described improvement in the art of kiln drying lumber in a dry kiln adapted for flatwise end piling: which improvement consists in arranging the lumber to be dried in two rows of iles, with a pile chimney in each row oi piles, with a central air passage between the two rows of piles, and with a side air passage between each row of piles and the adjacent side wall of the dry kiln; and subjecting the lumber to be dried to a reversible air circulation passing in a substantially lateral direction between the layers of lumber and in a substantially vertical direction through the pile chimneys, the central air passage, and the side air passages.

ROLF THELEN. 

